BioWare remains rather secretive about its next addition to the Mass Effect series, albeit they didn't hesitate to share a few details (tiny details). Fair enough, the first thing would be that they are, in fact, not prepared to share anything concrete about the game at this time.

However, a number of publications have reported that BioWare unveiled some details about Mass Effect 4 during this year's San Diego Comic Con. To begin with, the game will feature the return of the Mako.

Here's a brief report from the Escapist (there's a chick in the video as well):

The return of Mako is a good move. It shows that BioWare means to draw the attention back to galaxy exploration, which I quite liked in the original game (even though people complained about the planets looking generic and dull).